Systems and methods for multi-pair atm over dsl

ABSTRACT

At a transmitter, an ATM cell stream is received from the ATM layer and is distributed on a cell-by-cell bases across multiple DSL PHY&#39;s. At the receiver, the cells from each DSL PHY are re-combined in the appropriate order to recreate the original ATM cell stream, which is then passed to the ATM layer.

RELATED APPLICATION DATA

This application claims the benefit of and priority under 35 U.S.C.§119(e) to U.S. Patent Application Ser. No. 60/327,440, filed Oct. 5,2001, entitled “Multi-Pair ATM Over DSL,” which is incorporated hereinby reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The systems and methods of this invention generally relate tocommunication systems. In particular, the systems and methods of thisinvention relate to asynchronous transfer mode (ATM) over digitalsubscriber line (DSL).

2. Description of Related Art

FIG. 1 illustrates the conventional configuration of a system fortransporting ATM over DSL using a single latency ADSL configuration. Asof the time of filing, single latency is most common form of ADSLdeployment. Further details of this specific architecture can be foundin DSL Forum Recommendation TR-042, incorporated herein by reference inits entirety.

For the system illustrated in FIG. 1, the access node 10 serves as anATM layer multiplexer/concentrator between the ATM core network 2 andthe access network. As described in the above referenced DSL ForumRecommendation, for ATM systems, the channelization of differentpayloads is embedded within the ATM data stream using different virtualpaths (VP) and/or virtual channels (VC). In the downstream direction,the VP/VC Mux module 16 and VPI/VCI translation module 14 receive cellsfrom the core network interface element 12 and function to perform cellrouting based on a virtual path identifier (VPI) and/or virtual channelidentifier (VCI) to the appropriate ATU-C 18. In the upstream direction,the VP/VC Mux module 16 and the VPI/VCI translation module 14 functionto combine the cell streams from the ATU-C's 18 into a single ATM cellstream to the core ATM network 2.

The broadband network termination (B-NT) 100 performs the functions ofterminating the ADSL signal entering the user's premises via the twistedpair cable and the ATU-R 22 and provides either the T, S or R interfacetowards the premises distribution network/terminal equipment 4. Theaccess ATM module 26 and the VP/VC Mux module 24 perform the ATM layerfunctions to support the TC layers in the ATU-R. The broadband networktermination 100 may also contain VPI/VCI translation functions tosupport multiplex/demuliplex of VC's between the ATU-R 22 and thepremise distribution network/terminal equipment 4 on a VPI and/or VCIbases. The broadband network termination 100 may also comprise a PDN/TEinterface element 28 and SAR module 30 the functions of which are wellknown and will be omitted for sake of clarity.

SUMMARY OF THE INVENTION

The exemplary systems and methods of this invention combine multiple DSLPHY's, i.e., multiple twisted wire pairs, to, for example, generate ahigh data rate connection for the transport of an ATM cell streambetween the service provider and, for example, a DSL subscriber. The ATMcell stream may contain one or more payloads where each payload ischannelized within the ATM data stream using different virtual paths(VP) and/or virtual channels (VC). At a transmitter, the ATM cell streamreceived from the ATM layer is distributed on a cell-by-cell basesacross the multiple DSL PHY's. At the receiver, the cells from each DSLPHY are re-combined in the appropriate order to recreate the originalATM cell stream, which is then passed to the ATM layer.

Accordingly, aspects of the invention relate to ATM communications.

Additional aspects of the invention relate to transporting ATM over DSL,and more particularly over ADSL.

Additional aspects of the invention also relate to distributing ATMcells from a single ATM cell stream across multiple twisted wire pairs.

Further aspects of the invention relate to distributing ATM cells from asingle ATM cell stream across multiple DSL communication links.

Further aspects of the invention relate to varying data rates over themultiple twisted wire pairs over which distributed ATM cells aretransported.

These and other features and advantages of this invention are describedin, or apparent from, the following detailed description of theembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention will be described in detailed, withreference to the following figures, wherein:

FIG. 1 is a functional block diagram illustrating a conventional ATMover ADSL system;

FIG. 2 is a functional block diagram illustrating an exemplary systemfor transporting ATM over ADSL according to this invention;

FIG. 3 illustrates an exemplary functional block diagram of themulti-pair multiplexing transmitter according to this invention;

FIG. 4 illustrates a functional block diagram of a second exemplarymulti-pair multiplexing transmitter according to this invention;

FIG. 5 illustrates a functional block diagram of a third exemplaryembodiment of the multi-pair multiplexing transmitter according to thisinvention;

FIG. 6 illustrates a functional block diagram of an exemplary multi-pairmultiplexing receiver according to this invention;

FIG. 7 illustrates a functional block diagram of a second exemplarymulti-pair multiplexing receiver according to this invention;

FIG. 8 illustrates a functional block diagram of a third exemplarymulti-pair multiplexing receiver according to this invention;

FIG. 9 is a functional block diagram illustrating a fourth exemplarymulti-pair multiplexing receiver according to this invention;

FIG. 10 illustrates a functional block diagram of a fifth exemplarymulti-pair multiplexing receiver according to this invention;

FIG. 11 illustrates a functional block diagram of a fourth exemplarymulti-pair multiplexing transmitter according to this invention;

FIG. 12 is a functional block diagram illustrating a sixth exemplarymulti-pair multiplexing receiver according to this invention;

FIG. 13 illustrates a standard five byte ATM UNI header;

FIG. 14 illustrates an exemplary modified ATM header according to thisinvention; and

FIG. 15 is a flowchart outlining an exemplary embodiment of a method forcombining multiple DSL PHYs to transport an ATM cell stream between aservice provider and a subscriber.

DETAILED DESCRIPTION OF THE INVENTION

The exemplary systems and the methods of this invention will bedescribed in relation to digital subscriber line communications and moreparticularly to asymmetric digital subscriber line communications.However, to avoid unnecessarily obscuring the present invention, thefollowing description omits well-known structures and devices that maybe shown in block diagram form or otherwise summarized. For the purposesof explanation, numerous specific details are set forth in order toprovide a thorough understanding of the present invention. It should beappreciated however that the present invention may be practiced invariety of ways beyond the specific details set forth herein. Forexample, the systems and methods of this invention can generally beapplied to any type of communications system including wirelesscommunication systems, such as wireless LANs, power line communications,or any other systems or combination systems that use ATM.

Furthermore, while the exemplary embodiments illustrated herein show thevarious components of the communication system collocated, it is to beappreciated that the various components of the system can be located atdistant portions of distributed network, such as a telecommunicationsnetwork and/or the Internet, or within a dedicated ATM over DSL system.Thus, it should be appreciated that the components of the communicationsystem can be combined into one or more devices or collocated on aparticular node of a distributed network, such as a telecommunicationsnetwork. It will be appreciated from the following description, and forreasons of computational efficiency, that the components of thecommunication system can be arranged at any location within adistributed network without affecting the operation of the system.

Furthermore, it should be appreciated that the various links connectingthe elements can be wired or wireless links, or a combination thereof orany other know or later developed element(s) that is capable ofsupplying and/or communicating data to and from the connected elements.Additionally, the term module as used herein can refer to any know orlater developed hardware, software, or combination of hardware andsoftware that is capable of performing the functionality associated withthat element.

Additionally, although this invention will be described in relation toATM systems, the systems and methods of this invention can be applied toany transport protocol that uses cells or packets for transmittinginformation. Therefore, for example, the same methods can be used forthe bonding of PHYs that transport Ethernet or IP packets. Furthermore,although this invention will be described in relation to ATM transportedover DSL PHYs, other PHYs, such as cable, voice band modems, ATM-25, andthe like, can also be used.

FIG. 2 illustrates an exemplary multi-pair ATM over DSL system. Inparticular, the system comprises an access node 100, a broadband networktermination 200, an ATM core network 2 and premise distributionnetwork/terminal equipment 4. The access node 100 further comprises acore network interface element 110, a VPI/VCI translation module 120, aVP/VC Mux module 130, an ATU-C multi-pair multiplexer 140 and aplurality of ATM TC ATU-C modules 150. The broadband network termination200 further comprises a plurality of ATU-R ATM TCs 210, an ATU-Rmulti-pair multiplexer 220, a VP/VC Mux module 230, an access ATM module240, and a PDN/TE interface module 250. Furthermore, the systemcomprises a SAR and PDN function module 260, wherein the functions oflike components have been discussed in relation to FIG. 1.

The exemplary system illustrated in FIG. 2 distributes ATM cells from asingle ATM cell stream across multiple ADSL PHY links, i.e., multipletwisted wire pairs (1 to n). The ATM cell stream, also referred to asthe ATM stream, may comprise one or more payloads where each payload ischannelized within the ATM stream using different virtual paths (VP)and/or virtual channels (VC). This can effectively create, for example,a high data rate ATM connection between a service provider and an ADSLsubscriber.

In accordance with an exemplary embodiment of this invention, the ATU-Cmulti-pair multiplexer 140 is inserted between the VP/VC multiplexer 130and the ATU-C's 150 at the V-C interface in the access node 100.Additionally, the ATU-R multi-pair multiplexer 220 is added to thebroadband network termination 200 at the T-R interface. Both of thesemulti-pair multiplexers have transmitter and receiver sections (notshown) whose operations are comparable. The multi-pair multiplexertransmitter section performs the task of distributing cells from the ATMstream among multiple ATM cell substreams. Each ATM cell substream, alsoreferred to as an ATM substream, is forwarded a different ATU. Themulti-pair multiplexer receiver section performs the task of recombiningthe ATM substreams to regain the original ATM stream.

In the exemplary system illustrated in FIG. 2, two ADSL PHYs 160 and 170are “bonded” together to transport a single ATM cell stream. However, itshould be appreciated, that the number of ADSL PHYs “bonded” togethercan be easily expanded to any number (N≧2) of ADSL PHYs thereby, forexample, enabling higher ATM data rates. In addition to the two ADSLPHYs 160 and 170 that are bonded together, it should further beappreciated that in some instances in the same access node 100, otherADSL PHYs may be operating in the traditional way. Obviously, the ADSLPHYs operating the traditional way do not need to be connected to themulti-pair multiplexer 140. Thus, in general, it should be appreciatedthat any combination of “bonded” and unbonded, i.e. traditional, ADSLPHY's, may be configured between the access node 100 and the broadbandnetwork determination 200. Furthermore, it should be appreciated thatall of the ADSL PHYs can be bonded together.

In may ADSL systems, the logical interface between the ATM layer the PHYis based on UTOPIA Level 2 with a cell level handshake. This same UTOPIALevel 2 logical interface can also be used between the multi-pairmultiplexer and the ATM layer and also between the multi-pairmultiplexer and the PHY in the access node 100 and the broadband networktermination 200. Although, the above example and the remainder of thisdiscussion will be directed toward the multi-pair multiplexer functionsusing a ADSL PHY, any version of DSL that has an ATM-TC, e.g., VDSL,SHDSL, or the like, may be used instead of, or conjunction with, theADSL PHY.

FIG. 3 illustrates an exemplary multi-pair multiplexing transmitteraccording to this invention. The ATU-C and ATU-R multi-pair multiplexerbox provide the same basic transmitter and receiver functions and thuscan be summarized as one unit.

In particular, the exemplary multi-pair multiplexing transmitter 300illustrated in FIG. 3 provides, but not limited to, accepting a singleATM stream 310 from the ATM layer and distributing the cells among N ATMsubstreams 320, where N≧2. Furthermore, the multi-pair multiplexingtransmitter 300 maps each ATM cell substream to a different DSLconnection and provides as output these ATM cell substreams to theappropriate ADSL PHY (ATUx). For the exemplary multi-pair multiplexingtransmitter 300 illustrated in FIG. 3, the cells from the ATM stream 310are distributed amongst the ATM substreams 320 based on the data rate ofeach DSL PHY.

The configuration of the multi-pair multiplexing transmitter 300 can bevaried to, for example, provide an equal or unequal data rate on the DSLPHYs. FIG. 4 illustrates an exemplary embodiment where an equal datarate is applied to all of the DSL PHYs. In particular, if the data rateon all of the DSL PHYs is the same, then an equal number of ATM cellswill be transported over every PHY connection. In this case, themulti-pair multiplexing transmitter 300 sends the first ATM cell to ATU1330, the second ATM cell to ATU2 340, the third ATM cell to ATU3 350,and so on. For the multi-pair multiplexing transmitter 300 illustratedin FIG. 4, N=3 and an equal data rate on all DSL PHYs is illustrated,therefore the input ATM cells from the ATM stream 310, as discussedabove, are distributed equally and sequentially among the DSL PHYs.

For the multi-pair multiplexing transmitter 300 illustrated in FIG. 5,an unequal data rate is transported on the DSL PHYs. In particular, if adata rate on all the DSL PHYs is not equal, the ATM cells can be forwardto the DSL PHYs, at, for example, a ratio that matches the ratios of theavailable PHY data rates. If, for example, N=2, as illustrated in FIG.5, and the data rate of the first DSL PHY 360 is two times the data rateof the second PHY 370, then the multi-pair multiplexer 300 would send 2ATM cells to the first DSL PHY, i.e., cells 1 and 2, and then send 1 ATMcell to the second DSL PHY, i.e., cell 3. However, in general, thisbasic concept can be expanded at least to include the situation whereN>2 and to non-integer data rate ratios.

For example, in a two modem environment where there is a “high-speed”and a “low-speed” implementation, an exemplary ratio of N:1 where N=2 to8 can be specified. This means that the “high-speed” modem will haveeight times the cells as the “low-speed” modem. In this exemplaryconfiguration, there are eight cells of receiver FIFO meaning that theentire “high-speed” receiver could be empted before needing to servicethe “low-speed” receiver.

FIG. 6 illustrates an exemplary multi-pair multiplexing receiver 400.The exemplary multi-pair multiplexing receiver 400 provides, but is notlimited to, accepting multiple ATM cell substreams from different DSLPHYs and recombining the ATM cells from the different ATM cellsubstreams to recreate the original ATM stream, which is passed to theATM layer. In particular, and as illustrated in FIG. 6, a plurality ofATM substreams are received by the multi-pair multiplexing receiver 400and recombined into the original ATM stream. Specifically, as in themulti-pair multiplexing transmitter, the recombining of cells from theDSL PHYs depends on the data rates of the individual PHY connections. Asin the embodiment discussed in relation to FIG. 4, where all DSL PHYshad an equal data rate, the multi-pair multiplexing receiver 400 canperform the inverse of the transmitting multiplexer function andreconstruct the original ATM stream by taking one cell from each ATMsubstream and combining them in the appropriate order, as illustrated inFIG. 7.

Similarly, as illustrated in relation to the multi-pair multiplexingtransmitter 300 illustrated in FIG. 5, where the DSL PHYs had an unequaldata rate, if different ratios of data rates are used a variable numberof cells will be taken from each ATM substream to reconstruct theoriginal ATM stream in the multi-pair multiplexing receiver 400 asillustrated in FIG. 8.

Furthermore, an in addition to the changes in data rate that arepossible on the DSL PHYs, ATM cells transported over a DSL PHY can havedifferent end-to-end delay (latency) based on several parameters. Thispotential latency difference between bonded PHYs places implementationrequirements on the multi-pair multiplexer. In particular, themulti-pair multiplexer receiver must be able to reconstruct the ATMstream even if the ATM cells are not being received in the same order asthey where transmitted.

For example, some of the exemplary reasons for having different delaysover different DSL PHYs include, but are not limited, configurationlatency which is based on the configuration of the DSL transmissionparameters. Specifically, these parameters include the data rate, codingparameters, such as the coding method, codeword size, interleavingparameters, framing parameters, or the like.

ATM-TC latency is based on cell rate decoupling in the ATM-TC.Specifically, the ATM-TC block in ADSL transceivers performs cell ratedecoupling by inserting idle cells according to the ITU Standard I.432,incorporated herein by reference in its entirety. This means thatdepending on the ATU timing and the state of the ATU buffers, an ATMcell that is sent over a DSL PHY will experience non-constant end-to-enddelay (latency) through the PHY.

Wire latency is based on differences in the twisted wire pairs.Specifically, the DSL electrical signals can experience different delaysbased on the difference in length of the wire, the gauge of the wire,the number bridged taps, or the like.

Design latency is based on differences in the DSL PHY design.Specifically, the latency of the PHY can also depend on the designchosen by the manufacture.

Thus, as result of the different latencies in the PHYs, it is possiblethat an ATM cell that was sent over a DSL PHY may be received at themulti-pair multiplexing receiver after an ATM cell that was sent outlater on a different DSL PHY.

FIG. 9 illustrates an example of variable delay based on the embodimentdiscussed in relation to FIG. 4. Therefore, the exemplary multi-pairmultiplexing receiver 500 should be able to accommodate at least thesetypes of variations in delay. An exemplary method for dealing with theissue of delay is to have cell buffers (not shown) in the multi-pairmultiplexing receiver 500 that can provide the ability to compensate forthe variations in delay. As example, if there is a cell buffer that canhold several ATM cells on each input ATM substream path, the multi-pairmultiplexing receiver 500 can simply wait until, for example, cellnumber 1 comes in path number one, while path number two will buffercell number 2 and wait for cell number 1 to be received. This methodrequires a cell buffer on each ATM substream path at the input of themulti-pair multiplexing receiver 500. The size of the cell buffer can bedetermined by, for example, the maximum difference in latency betweenthe “bonded” PHYs. As an alternative, the buffer can be based on onelarge buffer with multiple pointers without effecting the operation ofthe system.

Another effective method of reducing the difference in latency betweenDSL PHYs is mandate that all DSL PHYs are configured with transmissionparameters in order to provide the same configuration latency. Anexemplary method of accomplishing the same configuration latency is byconfiguring the exact same data rate, coding parameters, interleavingparameters, etc. on all DSL PHYs. Alternatively, different PHYs canhave, for example, different data rates but use the appropriate codingor interleaving parameters to have the same latency on all the bondedPHYs.

As an example, for Reed Solomon coding and interleaving functions asdefined in ADSL standards G.992.1 and G.992.3, incorporated herein byreference in their entirety, the latency due to these functions isdefined as:

Latency=N*D/R,

where N is the number of bits in a codeword, D is the interleaver depthin codewords and R is the data in bits per second.

For example if N=1600 bits, i.e., 200 bytes, D=64 codewords andR=6400000 bps then:

Latency=1600*64/640000=0.016 seconds.

Therefore if, for example, two PHYs have different data rates, R1 and R2then, in order to bond these PHYs together and have the sameconfiguration latency set:

N1*D1/R1=N2*D2/R2,

where N1 and N2 are the bits in a codeword for each PHY and D1 and D2are the interleaver depths for each PHY.

This can also be rewritten as:

N1*D1=(R1/R2)*N2*D2.

Thus, in general, the N1, D1, N2 and D2 parameters must be chosen tosatisfy the above equations and this can be accomplished in severalways.

For example, if the configuration latency is specified as 0.016 seconds,and R1=6400000 bps and R2=1600000 then, as described in the exampleabove, N1 anss D1 can be configured as N1=1600 and D1=64. Therefore:

N2*D2=(R2/R1)*D1*N1=(1600000/6400000)*1600*64=1600*64/4.

Therefore, for example, N2 and D2 can be configured as (N2=1600, D2=16)or (N2=400, D2=64) or (N2=800, D2=32), etc.

Obviously the same methods can be applied to more than 2 PHYs withdifferent data rates.

The ATM-TC receiver in ADSL systems is specified to discard ATM cellsthat are received with an incorrect cyclic redundancy check, e.g.,(HEC). This means that if there are bit errors as the result oftransmission over the ADSL channel, ATM cells will be discarded by theATM-TC and not sent to the multi-pair multiplexing receiver. As a resultof this type of error condition, ATM cells may be received out of orderin the multi-pair multiplexing receiver.

FIG. 10 illustrates an exemplary multi-pair multiplexing receiver 500with a single ATM cell lost due to PHY channel errors using theexemplary embodiment discussed in relation to FIG. 4. In FIG. 10, ATMcell number 5 was discarded by the second DSL PHY 510 due to, forexample, a HEC error. Therefore, if the multi-pair multiplexing receiver500 is not aware of this error, the ATM cells stream can not bereconstructed appropriately.

The exemplary systems and methods of this invention utilize a multi-paircell counter to operate in the condition where the ATM cells arediscarded by DSL PHY when, for example, HEC errors occur. The multi-pairmultiplexing transmitter can embed the multi-pair cell counter in theheader of each ATM cell after receiving the ATM cell from the ATM layer.At the receiver, the multi-pair multiplexing receiver reads themulti-pair cell counter and removes it from the header of the ATM cellprior to sending the ATM cell to the ATM layer. The multi-pair cellcounter is a value that indicates the position of a particular ATM cellin the ATM cell stream.

In its simplest form, the multi-pair cell counter can be a modulo Lcounter that starts at, for example, zero and increments by one for eachconsecutive ATM cell up to a value L−1. For example, if L equals 256,the value of the multi-pair cell counter could start at zero andincrement by one up to a value of 255. After 255, the multi-pair countercould be started at zero again, and so on.

As previously discussed, the multi-pair cell counter can be embedded inthe ATM cell header of all the ATM cells in the ATM stream. FIG. 11illustrates the multi-pair multiplexing transmitter 400 as discussed inrelation to the example illustrated in FIG. 4, with L equal to 4 and themulti-pair cell counter specified inside the ATM cell header. At thereceiver, the multi-pair cell counter is read by the multi-pairmultiplexing receiver and removed from the ATM cell header. Themulti-pair multiplexing receiver uses the multi-pair cell counter toproperly recombine the ATM cells to reconstruct the ATM stream.Therefore, as in the example above, where a cell was discarded by theDSL PHY, the multi-pair multiplexing receiver would be able to determinethis error and the ATM cell(s) placed in the appropriate order.

FIG. 12 illustrates an example where the 5^(th) ATM cell in the ATMstream was discarded by the PHY. The 5^(th) ATM cell in the exemplaryATM stream has a multi-pair cell counter number equal to 0 and was senton the second ATU. The exemplary multi-pair multiplexing receiver 500can check the multi-pair cell count value of the ATU's ATM cell beforeinserting the cell back into the ATM stream. In this manner, when themulti-pair multiplexing receiver checks the ATM cell counter from thesecond ATU and reads a multi-pair cell count 3 instead of zero, themulti-pair multiplexing receiver can determine that the ATM cell withthe multi-pair cell counter equal to 0 was discarded by the second ATUPHY. In this case, multi-pair multiplexing receiver will not take a cellfrom the ATU-2 ATM substream. Instead, the multi-pair multiplexingreceiver will move to the next ATU in order to check the multi-pair cellcount value, and insert the ATM cell back into the ATM stream if themulti-pair cell count is correct, and continue. Therefore, as a resultof using the multi-pair cell counter, the multi-pair multiplexingreceiver can properly reconstruct the original ATM cell stream even inthe presence of ATM cell lost.

The exemplary main multi-pair cell parameter is the value of L. Theappropriate value of L depends on the number of bonded PHYs (N) and themaximum number (M) of consecutive ATM cells that may be discarded by thePHY. The design constraint on L is that it must be large enough so thatthe multi-pair multiplexing receiver can still detect cell lost evenwhen the maximum number of consecutive ATM cells are discarded by a PHY.This places the constraint that L>N*M. For example, if there are N=4bonded PHYs, and the maximum number of consecutive ATM cells that maydiscarded by the PHY is M=50, then L>200. If, for example L is chosen tobe equal to 256, then even when 50 consecutive ATM cells are lost, themulti-pair multiplexing receiver can accurately detect the error event.

There are several exemplary methods to embedding the multi-pair cellcounter into the ATM cell header including, but not limited to, usingthe GFC field in the UNI ATM header. The GFC field is currently not usedand is typically set to zero.

The GFC field is a four bit field therefore the maximum value of L is16. This could pose an issue when the channel has, for example, impulsenoise and the PHY data rate is high resulting in cases where multipleATM cells are often discarded by the PHY.

Therefore, as an alternative, bits in the VPI/VCI field can be used. TheVPI field occupies 8 bits in the UNI header and identifies the routetaken by the ATM cell. The VCI field occupies 16 bits in the UNI headerand it identifies the circuit or connection number on the path. In orderuse the VPI/VCI field for the multi-pair cell counter, the multi-pairmultiplexing transmitter overwrites bits in the VPI/VCI field with themulti-pair cell counter value on a cell by cell bases. At the receiver,the multi-pair multiplexing receiver reads the multi-pair cell countervalue and resets and overwrites the VPI/VCI back to the original value.

This method requires the multi-pair multiplexing receiver to haveknowledge of the overwritten VPI/VCI bits. As an example, this can beaccomplished by communicating the VPI/VCI fields of the ATM streamduring initialization/configuration of the DSL connection or duringconfiguration or re-configuration of the ATM connection. Since theVPI/VCI field has 24 bits, the L value for the multi-pair cell countercan be set to a very large number.

One exemplary method for embedding the multi-pair cell counter in theVPI/VCI field is to construct a table of all, or a portion of, possibleVPI/VCI values that may be transported by the bonded DSL PHYs. ThisVPI/VCI table can, for example, be stored in the multi-pair multiplexingtransmitters and receivers for all PHYs. The table maps a VPI/VCI valueto a table index value that is also stored in the multi-pairmultiplexing transmitters and receivers for all PHYs. If there are KVPI/VCI values being transported over the bonded DSL PHYs, the VPI/VCIvalue could be mapped to a number from zero to K−1. At the multi-pairmultiplexing transmitter, the VPI/VCI value in the ATM header isreplaced with the table index value. Since there are limited numbers ofVPI/VCI going to a single subscriber, the table index value can utilizeonly a fraction of the 24 bits available in the VPI/VCI field.Therefore, the multi-pair multiplexing transmitter can use the remainingVPI/VCI bits to transport, for example, the multi-pair cell counter.

At the receiver, the multi-pair multiplexing receiver is multi-pair cellcounter that reconstructs the ATM stream as discussed above.Additionally, the multi-pair multiplexing receiver can read the tableindex value in the ATM header and write the VPI/VCI value correspondingto the table index value as stored in the VPI/VCI table back into theVPI/VCI header field.

As a simple example, where only one VPI/VCI is being sent over thebonded DSL connection, the VPI/VCI table will have only one value.Therefore, in this case, it is not necessary to insert the table indexvalue at the transmitter. The transmitter may use the bits in theVPI/VCI field for the multi-pair cell counter. At the receiver, themulti-pair cell counter is read and used to reconstruct the ATM stream.Since only one VPI/VCI value is being used, the receiver can reset theVPI/VCI field to the appropriate value prior to sending the ATM streaminto the ATM layer. This approach can work, for example, with manyconsumer based employments of a DSL, since in most cases a singleVPI/VCI is used.

As an alternative, consider a four VPI/VCI situation.

TABLE 1 VPI/VCI Table VPI/VCI Value Table Index Value (TIV) Va (24 bitvalue) 0 Vb (24 bit value) 1 Vc (24 bit value) 2 Vd (24 bit value) 3

Table 1 contains an exemplary VPI/VCI table with four VPI/VCI addresses.Additionally, for the purpose of this example, the multi-pair cellcounter is specified to be an eight bit counter, i.e., a modulo 255counter.

FIG. 13 illustrates the format for the standard five bit ATM UNI header.The VPI/VCI values in Table 1 corresponds to the 24 bit VPI/VCI valuesin the UNI ATM header.

FIG. 14 illustrates an exemplary format of the ATM header after themulti-pair multiplexing transmitter has replace the VPI/VCI values withthe table index value and then embedded the multi-pair cell counter inthe VPI/VCI field. The first two bits the VPI/VCI field are used totransport the table index value (TIV) and the next eight bits are usedto transport the multi-pair cell counter. The remaining bits can bereserved and can be used, for example, by the multi-pair multiplexingblocks for other purposes, such as the transportation of messagesbetween the multi-pair multiplexing blocks, or the like.

At the receiver, the multi-pair multiplexing receiver reads themulti-pair cell counter value from the header in order to properlyreconstruct the ATM stream. The multi-pair multiplexing receiver alsoreads the TIV in the ATM header and writes the VPI/VCI corresponding tothe table index value as stored in the VPI/VCI table back into theVPI/VCI header field. As a result, at the output of the multi-pairmultiplexing receiver, the ATM header can be completely reconstructedinto the standard UNI format comprising the original data contents.

In this illustrative example, there were four VPI/VCI addresses beingused in cells being transported over the bonded ADSL system. However, inmany deployments, the VP is determined in the DSLAM, which means thatthe VPI field is the same for all packets. Therefore, in the case ofterminating the VP and the DSLAM, the VP field could, for example, beused in transporting the TIV.

FIG. 15 illustrates an exemplary method of transporting ATM over DSL. Inparticular control begins in step S100 and continues to step S110. Instep S110 the cell distributions are determined, for example, based ondiffering data rates between the DSL PHYs, or the like. Next, in stepS120 the cells from the ATM stream are assigned based on the determinedcell distribution to the appropriate ATM TC cell stream. Then, in stepS130, the cells are transmitted to a receiver. Control then continues tostep S140.

In step S140, a receiver receives the cells. Next, in step S150, the ATMsubstreams are combined to reconstruct the ATM stream. In particular, instep S152, a determination is made whether there is a difference inlatency between the DSL lines. If there are differential latencyproblems, control continues to step S154 where the differential latencyis compensated for by, for example, buffering, or the like. Otherwise,control jumps to step S156.

In step S156, a determination is made whether other errors are presentin one or more of the substreams. If other errors, such as droppedcells, channel bit errors, or the like are present, control continues tostep S158 where the other errors are compensated for. Otherwise, controljumps to step S160 where the control sequence ends.

The above-described ATM over DSL system can be implemented on atelecommunications device, such a modem, a DSL modem, an ADSL modem, amulticarrier transceiver, a VDSL modem, or the like, or on a separateprogrammed general purpose computer having a communications device.Additionally, the systems and methods of this invention can beimplemented on a special purpose computer, a programmed microprocessoror microcontroller and peripheral integrated circuit element(s), an ASICor other integrated circuit, a digital signal processor, a hard-wiredelectronic or logic circuit such as discrete element circuit, aprogrammable logic device such as PLD, PLA, FPGA, PAL, modem,transmitter/receiver, or the like. In general, any device capable ofimplementing a state machine that is in turn capable of implementing theflowchart illustrated herein can be used to implement the various ATMover DSL methods according to this invention.

Furthermore, the disclosed methods may be readily implemented insoftware using object or object-oriented software developmentenvironments that provide portable source code that can be used on avariety of computer or workstation platforms. Alternatively, thedisclosed ATM over DSL system may be implemented partially or fully inhardware using standard logic circuits or VLSI design. Whether softwareor hardware is used to implement the systems in accordance with thisinvention is dependent on the speed and/or efficiency requirements ofthe system, the particular function, and the particular software orhardware systems or microprocessor or microcomputer systems beingutilized. The ATM over DSL systems and methods illustrated hereinhowever can be readily implemented in hardware and/or software using anyknown or later developed systems or structures, devices and/or softwareby those of ordinary skill in the applicable art from the functionaldescription provided herein and with a general basic knowledge of thecomputer and telecommunications arts.

Moreover, the disclosed methods may be readily implemented in softwareexecuted on programmed general purpose computer, a special purposecomputer, a microprocessor, or the like. In these instances, the systemsand methods of this invention can be implemented as program embedded onpersonal computer such as JAVA® or CGI script, as a resource residing ona server or graphics workstation, as a routine embedded in a dedicatedATM over DSL system, or the like. The ATM over DSL system can also beimplemented by physically incorporating the system and method into asoftware and/or hardware system, such as the hardware and softwaresystems of a communications transceiver.

It is, therefore, apparent that there has been provided, in accordancewith the present invention, systems and methods for ATM over DSL. Whilethis invention has been described in conjunction with a number ofembodiments, it is evident that many alternatives, modifications andvariations would be or are apparent to those of ordinary skill in theapplicable arts. Accordingly, it is intended to embrace all suchalternatives, modifications, equivalents and variations that are withinthe spirit and scope of this invention.

1. A communication system that allows the transmission of ATM over acommunications link comprising: an ATM stream; a transmitter multi-pairmultiplexer module, a receiver multi-pair multiplexer module; and aplurality of ATM substreams each associated with a multiple twisted wirepair, wherein the ATM stream is distributed between the plurality of ATMsubstreams. 2-13. (canceled)